JP2018183801A - Substrate manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a substrate manufacturing method capable of easily obtaining a thin magnesium oxide single crystal substrate with few lattice defects. SOLUTION: A first step of arranging a laser condensing means for condensing a laser beam on a surface to be irradiated 20r of a magnesium oxide single crystal substrate 20 in a non-contact manner, and using the laser condensing means, a predetermined irradiation condition. Then, while irradiating the surface of the magnesium oxide single crystal substrate 20 with laser light to collect the laser light inside the single crystal member, the laser focusing means and the magnesium oxide single crystal substrate 20 are relatively moved in a two-dimensional manner. By doing so, a second step of sequentially forming planar scratches by sequentially forming processing marks inside the single crystal member is provided. [Selection diagram] Figure 2

Description

  The present invention relates to a substrate manufacturing method optimal for manufacturing a thin magnesium oxide single crystal substrate.

  Magnesium oxide single crystal substrates are used in the semiconductor field, display field, energy field, and the like. In order to manufacture this magnesium oxide single crystal substrate, it is known to grow a crystal in bulk and cut it into a substrate, or epitaxially grow into a thin film (see, for example, Patent Document 1).

  On the other hand, diamond is considered as a semiconductor suitable for high-frequency and high-power electronic devices, and a magnesium oxide substrate or a silicon substrate is used as a base substrate in a vapor phase synthesis method that is one of the synthesis methods (for example, Patent Document 2).

JP 2001-080996 A Japanese Patent Laying-Open No. 2015-59069

  In recent years, with the improvement in performance of semiconductor devices, a thin magnesium oxide single crystal substrate with few lattice defects is increasingly required.

  A magnesium oxide substrate (MgO substrate) which is a base substrate in the production of the above diamond substrate is expensive. For example, after a single crystal diamond is vapor-phase synthesized, the magnesium oxide substrate is peeled off while leaving a necessary thickness as a base substrate. By separating, the magnesium oxide substrate can be reused as a base substrate. Specifically, for example, if a magnesium oxide substrate with a thickness of 180 μm is obtained from a base substrate of magnesium oxide with a thickness of 200 μm and reused, a significant cost reduction can be achieved in the diamond substrate manufacturing process, greatly contributing to the cost reduction of the diamond substrate. Can be expected to do.

  In view of the above problems, an object of the present invention is to provide a substrate manufacturing method capable of easily obtaining a thin magnesium oxide single crystal substrate.

  By the way, various manufacturing methods for obtaining a single crystal silicon substrate have been proposed. As a result of intensive studies, the present inventor has adopted a new processing principle different from single crystal silicon for a magnesium oxide substrate in the present invention. A manufacturing method based on this was found.

  According to one aspect of the present invention for solving the above problems, a first step of disposing laser condensing means for condensing laser light in a non-contact manner on an irradiated surface of a magnesium oxide single crystal member; Using the laser condensing means, the laser condensing means and the single crystal member while condensing the laser light inside the single crystal member by irradiating the surface of the single crystal member with laser light under a predetermined irradiation condition A substrate manufacturing method is provided that includes a second step of sequentially forming planar marks by sequentially forming processing marks in the single crystal member by relatively moving the substrate in two dimensions. Is done.

  According to another aspect of the present invention, a laser condensing means for condensing laser light is disposed in a non-contact manner on the irradiated surface of the magnesium oxide single crystal member, and the laser concentrator Two-dimensionally connecting the laser condensing means and the single crystal member while irradiating the surface of the single crystal member with laser light under a predetermined irradiation condition and condensing the laser light inside the single crystal member. A second step of sequentially forming a processing mark inside the single crystal member by moving the laser beam relative to the surface of the single crystal member, and a laser on the surface of the single crystal member under a predetermined irradiation condition using the laser focusing means. When irradiating in the second step by irradiating light and condensing laser light inside the single crystal member while moving the laser condensing means and the single crystal member relatively in a two-dimensional manner Sequential irradiation of laser light between adjacent irradiation lines The third substrate manufacturing method that includes a step of sequentially cause surface delamination by gradually is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate manufacturing method which can obtain a thin magnesium oxide single crystal substrate easily can be provided.

(A) is a typical perspective view of the peeling substrate manufacturing apparatus used by one Embodiment of this invention, (b) is the elements on larger scale of the peeling substrate manufacturing apparatus used by one Embodiment of this invention. . In one Embodiment of this invention, it is typical sectional drawing explaining the peeling board | substrate peeling from the magnesium oxide single crystal substrate. In Example 1, it is explanatory drawing which shows the irradiation conditions of a laser beam. In Experimental Example 2, it is explanatory drawing which shows the irradiation conditions of a laser beam. In Experimental Example 2, it is an imaging diagram showing a test piece plane after irradiation with laser light. In Experimental Example 2, it is an imaging diagram showing a test piece plane after irradiation with laser light. In Experimental Example 2, it is an imaging diagram showing a test piece plane after irradiation with laser light. In Experimental Example 2, it is an imaging diagram showing a test piece plane after irradiation with laser light. In Experimental example 2, it is an imaging figure which shows the test piece cross section after irradiation of a laser beam. In Experimental example 2, it is an imaging figure which shows the test piece cross section after irradiation of a laser beam. In Experimental example 2, it is an imaging figure which shows the test piece cross section after irradiation of a laser beam. In Experimental example 2, it is an imaging figure which shows the test piece cross section after irradiation of a laser beam. In Example 3, it is explanatory drawing which shows the irradiation conditions of a laser beam. In Experimental example 3, it is a photograph figure which shows the wafer plane after irradiation of a laser beam. In Experimental Example 3, it is a schematic plan view for explaining a region to be cleaved from a wafer after irradiation with laser light. In Experimental example 3, it is a photograph figure which shows the additional cleaving member obtained by cleaving the wafer after irradiation of a laser beam, and further cleaving. In Experimental example 3, it is a photograph figure of the elongate member obtained by cleaving the wafer after irradiation of a laser beam. In Experimental example 3, it is a photograph figure of the elongate member obtained by cleaving the wafer after irradiation of a laser beam. FIG. 10 is an explanatory diagram illustrating cutting out a test piece from a single crystal magnesium oxide wafer in Experimental Example 4. (A)-(c) is the example 4 of an experiment, respectively, The typical top view explaining that irradiating a laser beam, typical sectional drawing, and the description explaining the irradiation conditions of a laser beam FIG. In Experimental example 4, it is a photograph figure which shows the peeling surface of a test piece. It is explanatory drawing explaining moving the imaging position of a peeling surface sequentially in Experimental example 4. FIG. In Experimental example 4, it is explanatory drawing explaining the state of a peeling surface by moving the imaging | photography position of a peeling surface sequentially, and imaging | photography. In Experimental example 4, it is an imaging figure obtained by image | photographing the cloudiness part of a peeling surface. In Experimental example 4, it is an imaging figure obtained by image | photographing the transparent part of a peeling surface. In Experimental example 4, it is an imaging figure obtained by image | photographing the interference part of a peeling surface. In Experimental example 4, it is explanatory drawing explaining the measurement position of the surface height of a peeling surface. In Example 4, it is explanatory drawing explaining the measurement result of the surface height of a peeling surface. In Experimental example 5, it is an imaging figure which shows the board | substrate surface when a laser beam is irradiated twice to the same area | region. In Experimental example 5, it is an imaging figure which shows a board | substrate cross section when a laser beam is irradiated twice to the same area | region. (A) And (b) is a schematic plan view explaining that the irradiation position of the laser beam is shifted in the second embodiment and Experimental Example 6, respectively, and a modified layer is formed by irradiation. It is a typical board | substrate sectional drawing explaining what was done. It is explanatory drawing explaining the irradiation conditions of a laser beam in Experimental example 6. FIG. (A) And (b) is the photograph figure which shows the test piece surface after completion of irradiation of a laser beam in Experimental example 6, respectively, and the elements on larger scale of (a). In Experimental example 6, it is a photograph figure which shows the peeling surface of a test piece. (A) And (b) is the image pick-up figure which shows the peeling surface of a test piece, and the elements on larger scale of (a) in Experimental example 6, respectively. In Experimental example 6, it is explanatory drawing explaining the measurement position of the surface height of the peeling surface of a test piece, and a measurement result.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the same or similar components as those already described are denoted by the same or similar reference numerals, and detailed description thereof is omitted as appropriate. The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not something specific. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention.

[First Embodiment]
First, the first embodiment will be described. In this embodiment, a release substrate is obtained from a single crystal substrate (single crystal member) using the release substrate manufacturing apparatus 10 (see FIG. 1).

  The release substrate manufacturing apparatus 10 includes an XY stage 11, a substrate mounting member 12 (for example, a silicon wafer) held on the stage surface 11f of the XY stage 11, and a magnesium oxide single unit mounted on the substrate mounting member 12. Laser condensing means 14 (for example, a condenser) that condenses the laser beam B toward the crystal substrate 20 is provided. In FIG. 1, the magnesium oxide single crystal substrate 20 is drawn in a rectangular shape in plan view, but it may of course be a wafer shape, and the shape can be freely selected.

  The XY stage 11 can adjust the height position (Z-axis direction position) of the stage surface 11f, and the distance L between the stage surface 11f and the laser focusing means 14 can be adjusted, that is, on the stage surface 11f. The distance between the single crystal substrate and the laser focusing means 14 can be adjusted.

  In the present embodiment, the laser condensing means 14 includes a correction ring 13 and a condensing lens 15 held in the correction ring 13, and an aberration caused by the refractive index of the magnesium oxide single crystal substrate 20 is reduced. It has a function of correcting, that is, a function as an aberration correction ring. Specifically, as shown in FIG. 1B, when the condenser lens 15 is condensed in the air, the laser light B reaching the outer peripheral portion E of the condenser lens 15 is reflected by the condenser lens 15. Correction is performed so that the laser beam B that has reached the center M is condensed on the condenser lens side. That is, when the light is condensed, the condensing point EP of the laser beam B reaching the outer peripheral portion E of the condensing lens 15 is compared with the condensing point MP of the laser beam B reaching the central portion M of the condensing lens 15. Correction is performed so that the position is close to the condenser lens 15.

  The condensing lens 15 includes a first lens 16 that condenses in the air, and a second lens 18 that is disposed between the first lens 16 and the single crystal substrate 20. In the present embodiment, each of the first lens 16 and the second lens 18 is a lens capable of condensing the laser beam B in a conical shape. Then, by adjusting the rotational position of the correction ring 13, that is, by adjusting the distance between the first lens 16 and the second lens 18, the distance between the condensing point EP and the condensing point MP can be adjusted. The laser focusing means 14 has a function as a lens with a correction ring.

  As the first lens 16, in addition to a spherical or aspherical single lens, it is possible to use a combination lens in order to secure various aberration corrections and working distances.

(Substrate manufacturing method)
Hereinafter, an example of manufacturing a thin magnesium oxide single crystal substrate from a magnesium oxide single crystal substrate will be described with reference to the accompanying drawings.

  In the present embodiment, the first step of arranging the laser condensing means 14 in a non-contact manner on the irradiated surface 20r of the magnesium oxide single crystal substrate 20 (hereinafter simply referred to as the single crystal substrate 20) with few lattice defects is performed. Although not shown, when a magnesium oxide substrate is peeled off while leaving a thin substrate of a magnesium oxide substrate on a diamond substrate formed using a magnesium oxide substrate as a base substrate, laser irradiation may be performed from the magnesium oxide substrate side.

  Then, using the laser condensing means 14, the laser condensing means 14 and the single crystal are condensed while condensing the laser light B inside the single crystal substrate 20 by irradiating the surface of the single crystal substrate 20 with the laser light B under predetermined irradiation conditions. By moving the substrate 20 relative to each other in a two-dimensional manner, processing marks K (for example, see FIG. 10) are sequentially formed in the single crystal substrate 20 to sequentially cause planar peeling. The second step is performed.

  In this second step, in consideration of the thickness of the peeling substrate 20p (see FIG. 2) manufactured by the above-described planar peeling, the surface to be irradiated of the single crystal substrate 20 is focused on a predetermined height position. The relative distance between the laser condensing means 14 and the single crystal substrate 20 is set in advance so as to focus on a predetermined depth position from 20r.

  In this embodiment, by sequentially forming the processing marks K, planar peeling occurs naturally, and the peeling substrate 20p is formed on the irradiated surface side. In this way, the predetermined irradiation condition of the laser beam B is set in advance so that the surface peeling occurs naturally. In setting the predetermined irradiation conditions, irradiation is performed in consideration of the properties (crystal structure and the like) of the single crystal substrate 20, the thickness t (see FIG. 2) of the separation substrate 20p to be formed, the energy density of the laser beam B at the focal point, and the like. The wavelength of the laser beam B, the aberration correction amount (defocus amount) of the condenser lens 15, the laser output, the dot pitch dp of the processing mark K (see FIG. 2, the interval between adjacent processing marks, ie, one Various values are set such as an interval between the machining trace and the machining trace formed immediately before it, a line pitch rp (see FIG. 1, an offset pitch, an interval between adjacent machining trace rows). Thereafter, the obtained release substrate 20p is subjected to post-treatment such as polishing of the release surface as necessary. In addition, planar peeling in this specification is a concept including a state where peeling is performed by applying a slight force even if peeling is not actually performed.

  According to this embodiment, a thin magnesium oxide single crystal substrate can be easily obtained.

  In the present embodiment, the laser beam B is preferably a high-intensity laser beam. In the present invention, high-intensity laser light is specified by peak power and power density that is power per unit area of energy per unit time. In order to further increase the power density, a laser with a short pulse width is preferable.

  In the present embodiment, the aberration correction can be adjusted by the correction ring 13 and the condensing lens 15 included in the laser condensing unit 14, and in the second step, the defocus amount can be set by adjusting the aberration correction. . Thereby, the range of said predetermined irradiation conditions can be expanded greatly. This defocus amount can be selected by means of adjusting the formation depth of the processing trace according to the thickness of the processed substrate or the thickness of the substrate to be peeled, and the conditions for forming the processing trace thinly, and magnesium oxide to be processed When the thickness of the substrate is 200 to 300 μm, the above range can be effectively expanded by setting the defocus amount to a range of 30 to 120 μm.

[Second Embodiment]
Next, a second embodiment will be described. In this embodiment, laser light irradiation is performed in two stages as compared to the first embodiment (see FIG. 31).

  In the present embodiment, as in the first embodiment, first, the first step of disposing the laser condensing means 14 in a non-contact manner on the irradiated surface 20r of the single crystal substrate 20 (magnesium oxide single crystal substrate) is performed.

  Then, the second step is performed. In this second step, the laser condensing unit 14 is used to irradiate the surface of the single crystal substrate 20 with the laser beam B under a predetermined irradiation condition to condense the laser beam inside the single crystal substrate 20. And the single crystal substrate 20 are relatively moved in a two-dimensional manner to sequentially form processing marks in the single crystal substrate 20.

  Thereafter, the third step is performed. In the third step, the laser condensing unit 14 is used to irradiate the surface of the single crystal substrate 20 with laser light under a predetermined irradiation condition and condense the laser light B inside the single crystal substrate 20. 14 and the single crystal substrate 20 are moved relative to each other in a two-dimensional manner, so that laser beam is sequentially irradiated between the adjacent irradiation lines R1 when irradiated in the second step, thereby removing the planar peeling. It will be generated sequentially.

  The predetermined irradiation condition in the second irradiation (third step) may or may not be the same as that in the first irradiation (second step).

  According to this embodiment, it is possible to further easily cause uniform and favorable peeling over the entire surface as compared with the first embodiment.

  In the third step, uniform peeling is easily generated efficiently by sequentially irradiating a laser beam to an intermediate position between adjacent irradiation lines R1.

  Further, in the second step and the third step, the modified layer 32 (see FIG. 31B) in which the processing marks are arranged in a plane is formed, and in the third step, planar peeling is sequentially generated. When going, a predetermined processing step in the second step is performed so that a uniform processing mark separation portion Kp formed by separation of processing marks is formed on the separation surface of the modified layer 32 opposite to the irradiated side. The irradiation conditions and the predetermined irradiation conditions in the third step may be determined in advance. Thereby, it becomes more remarkable that it becomes easy to produce uniform and favorable peeling over the whole surface.

<Experimental example 1>
The inventor uses the release substrate manufacturing apparatus 10 described in the above embodiment to hold a silicon wafer as the substrate mounting member 12 on the stage surface 11f on the XY stage 11, and the single crystal substrate 20 is placed on the silicon wafer. A single crystal magnesium oxide wafer 20u (hereinafter simply referred to as wafer 20u) was placed and held.

  Then, with the substrate manufacturing method described in the above embodiment, a laser is applied to each irradiation experiment region of the wafer 20u from the irradiated surface side in order to sequentially form the processing marks K inside each irradiation experiment region of the wafer 20u. While irradiating the light B, the laser condensing means 14 and the wafer 20u were moved relatively two-dimensionally (planar).

  In this experimental example, a single processing trace row is formed by irradiating the laser beam B in a line shape (in a straight line), and the processing traces are parallel to the processing trace row at positions separated by a predetermined amount of offset intervals. Rows were formed, and processing trace rows were similarly formed at positions separated by a predetermined amount of offset intervals. In this experimental example, laser light irradiation experiments were performed for laser light B having wavelengths of 1064 nm, 532 nm, and 1024 nm, respectively. Irradiation conditions are shown in FIG.

  As a result of observing the irradiated surface with an electron microscope after irradiation, at 1064 nm, the laser beam B did not enter the wafer 20u so much and ablation occurred on the wafer surface. At 532 nm, the laser beam B was incident on the wafer 20u and a processing trace was formed inside the wafer, but it was not a very good processing trace because the irradiation energy was too strong. At 1024 nm, the laser beam B was incident on the wafer 20u and a processing trace was formed inside the wafer, which was a relatively good processing trace.

<Experimental example 2>
As in Experimental Example 1, the present inventor uses the release substrate manufacturing apparatus 10 described in the above embodiment to hold a silicon wafer on the stage surface 11f on the XY stage 11, and forms a single crystal substrate 20 on the silicon wafer. Wafer 20u (single crystal magnesium oxide wafer, crystal orientation 100, diameter 50.8 mm, thickness 300 μm) was placed and held.

  Then, while irradiating each irradiation experimental region of the wafer 20u with the laser beam B, the laser condensing means 14 and the wafer 20u are relatively moved in a planar shape (two-dimensional shape), so that each irradiation experimental region is inside. Processing marks K (see, for example, FIG. 11) were sequentially formed. In Experimental Example 1, three machining traces were formed, but in this Experimental Example, 100 machining traces were formed. Irradiation conditions are shown in FIG.

  In this experimental example, based on the result of Experimental Example 1, the wavelength of the laser beam B to be irradiated was set to 1024 nm. Further, the defocus amount (DF) was set to 0.05 mm, and the processing marks K were formed in a line shape (linear shape) at substantially the middle position in the thickness direction of the wafer 20u. At that time, the laser output was changed as a parameter, and irradiation was performed at 0.1 W, 0.3 W, 0.5 W, and 1.0 W, respectively. Planar imaging diagrams of each test piece after irradiation are shown in FIGS. In addition, in the case where a striped pattern SP (rainbow pattern) is generated on each test piece surface side in FIGS. 6 to 8, it is implied that the test piece surface side is deformed by the propagation of cracks inside the test piece. doing.

  Then, in order to investigate the generation | occurrence | production state of the crack by the process mark K, it cleaved as a test piece so that the process mark K might be exposed for every irradiation experiment area | region, and the side surface cross section was observed. 9 to 12 are side cross-sectional imaging diagrams of each test piece. In addition, when the striped pattern SP (rainbow pattern) has arisen on each test piece surface side, it has implied that the test piece surface side is deform | transforming because a crack propagates inside a test piece.

  At a laser output of 0.1 W, a processing mark K was formed inside the test piece, but no crack propagation occurred. At a laser output of 0.3 W, a processing mark K was formed inside the test piece and crack propagation occurred, but peeling at the crack propagation portion was not observed. When the laser output was 0.5 W, a processing mark K was formed inside the test piece, crack propagation occurred, and peeling at the crack propagation portion was observed. At a laser output of 1.0 W, a processing mark K was formed inside the test piece, crack propagation also occurred, and peeling at the crack propagation part was observed. However, damage to the peeling surface may be due to excessive irradiation energy. It was seen.

<Experimental example 3>
Based on the result of Experimental Example 2, the present inventor conducted the Experimental Example with the laser output set to 0.5 W.

  In this experimental example, similarly to Experimental Example 2, the release substrate manufacturing apparatus 10 described in the above embodiment is used, a silicon wafer is held on the stage surface 11f on the XY stage 11, and the single crystal substrate 20 is formed on the silicon wafer. Wafer 20u (single crystal magnesium oxide wafer) was placed and held.

  Then, by moving the laser condensing means 14 and the wafer 20u relatively in a plane (two-dimensional), the wafer 20u was irradiated with the laser beam B in a plane to form a processing trace row. Irradiation conditions are shown in FIG.

  In this experiment example, when the laser beam B is irradiated, the line pitch rp is changed as a parameter, and the irradiation regions 20a to 20c (see FIG. 14) are irradiated so that the line pitch rp becomes 10 μm, 20 μm, and 50 μm, respectively. did.

  And each irradiation area was cut and it was set as the test piece. In this cleaving, all are cleaved using a glass cutter so as to become a long and narrow member having a short width W1 (corresponding to the member shown by the dot hatched area A in FIG. 15) elongated in the direction along the orientation flat. The final test piece is a member obtained by cutting off both ends of the elongated member in the longitudinal direction so as to leave the central portion of the width W2 constituting the longitudinal central portion of the elongated member.

  When the line pitch rp was 50 μm, natural peeling did not occur from the irradiated surface side even when the line pitch rp was cleaved into the elongated member. In this specification, the term “natural separation from the irradiated surface side of the substrate” means that the substrate is peeled in two dimensions as a separation substrate on the irradiated surface side without applying force to the irradiated surface side of the substrate. .

  Then, the elongated member was further cleaved to obtain a final test piece TP (see FIG. 16). Even in this final test piece TP, natural peeling did not occur from the irradiated surface side.

  When the line pitch rp is 20 μm, when the final test piece is cleaved, as shown in FIG. 17, the peeling substrate 20 p is naturally peeled in the half area of the irradiated surface 20 r (half area of the area A). It was found that natural peeling occurred in a half region of the irradiated surface 20r. In the remaining half of the area, the peeling substrate 20p did not spontaneously peel, but it was confirmed that it was completely peeled from the elongated member body 20m (see FIG. 2). Note that FIG. 17 shows a peeled substrate 20p that is naturally peeled in a half region of the irradiated surface 20r, and the remaining test piece TPm covered with a protective film.

  When the line pitch rp is 10 μm, the final test piece is cleaved, and as shown in FIG. 18, the release substrate is naturally cracked in the entire area of the irradiated surface 20r (all areas of the area A), and the elongated member body 20m. (See FIG. 2). Therefore, it was confirmed that the peeling substrate 20p was completely peeled from the elongated member body 20m. FIG. 18 shows a peeling substrate 20p that is naturally cracked and peeled naturally from the entire area of the irradiated surface 20r, and the remaining test piece TPm covered with a protective film.

<Experimental example 4>
As shown in FIG. 19, the present inventor used a single crystal magnesium oxide substrate (hereinafter referred to as test piece J1) having a square shape in plan view of 10 mm square from a single crystal magnesium oxide wafer 20u having a diameter of 2 inches and a thickness of 300 μm. Cut out. In addition, as shown in FIG. 19, the single crystal magnesium oxide wafer 20u and the test piece J1 were subjected to an experiment with corresponding crystal orientations (100, 010, etc.). The direction in which cleavage is easy is the crystal orientation 100 (plane orientation 100).

(1) Irradiation conditions In this experimental example, using the release substrate manufacturing apparatus 10 described in the above embodiment, as shown in FIG. 20A, a processing mark 22c is formed at a predetermined depth position of the test piece J1. The planar modified layer 22 was formed inside the test piece J1 by forming with the dot pitch dp and the line pitch rp. FIG. 20B shows a schematic cross-sectional view of the test piece J1 on which the machining mark 22c is formed, and FIG. 20C shows the irradiation condition of the laser beam.

(2) Release surface After irradiation with laser light, the irradiated surface side (upper side) of the test piece J1 was sandwiched between aluminum bases 24u and 24b via an adhesive. The pedestals 24u and 24b are both made of aluminum. An epoxy adhesive was used as the adhesive, and the base 24u was bonded to the irradiated surface side (upper side) of the test piece J1, and the base 24b was bonded to the bottom side (lower side) of the test piece J1.

  Then, by pulling the pedestals 24u, 24b in the vertical direction, the peeling force from the modified layer 22 is measured, and the irradiated surface side (upper side) of the test piece J1 is provided from the modified layer 22. The tensile rupture stress required to separate the upper test piece J1u and the lower test piece J1b having the bottom side (lower side) of the test piece J1 was calculated. As a result, separation was possible with a tensile stress of 0.3 MPa. Therefore, it could be separated from the modified layer 22 with a significantly smaller tensile rupture stress than 12 MPa, which is the tensile rupture stress of the single crystal silicon substrate.

  The inventor was able to observe with the naked eye that a striped pattern was formed on the peeling surface J1us of the upper test piece J1u and the peeling surface J1bs of the lower test piece J1b (see FIG. 21).

  Then, the peeling surface J1bs of the lower test piece J1b was photographed with an SEM (scanning electron microscope) while sequentially shifting the imaging position from point P1 to point P2 shown in FIG. An imaging result is shown in FIG. In addition, in the imaging drawing attached to this specification, a crystal orientation is also shown suitably.

  On the peeling surface J1bs, a periodic pattern J1bp was formed so that a cloudy portion J1bw, a transparent portion (smooth portion) J1bt, and an interference portion J1bi appeared in order. Here, the cloudy portion J1bw extends in the direction of the crystal orientation 011 and the direction in which the periodic pattern J1bp continues is the direction of the crystal orientation 01-1. Further, a large step BB (about 16 μm) was formed in the cloudy portion J1bw, and a smooth surface F was formed in the transparent portion (smooth portion) J1bt.

  Further, the present inventor has photographed the cloudy portion J1uw of the peeling surface J1us of the upper test piece J1u and the cloudy portion J1bw of the peeling surface J1bs of the lower test piece J1b, taking the SEM photographing magnification. The imaging results are shown in FIG. The crystal orientation in FIG. 24 is the same as the crystal orientation shown in FIG.

  Moreover, the transparent part (smooth part) J1ut of the peeling surface J1us of the upper test piece J1u and the transparent part (smooth part) J1bt of the peeling surface J1bs of the lower test piece J1b were photographed. An imaging result is shown in FIG.

  Moreover, the interference part J1ui of the peeling surface J1us of the upper test piece J1u and the interference part J1bi of the peeling surface J1bs of the lower test piece J1b were photographed. The photographing result is shown in FIG. The crystal orientation in FIG. 26 is the same as the crystal orientation shown in FIG.

  24 to 26, both the peeling surface J1us of the upper test piece J1u and the peeling surface J1bs of the lower test piece J1b were photographed at both 1000 times and 10,000 times.

  With respect to the peeling surface J1bs of the lower test piece J1b, as shown in FIG. 24, large holes BH are irregularly formed in the cloudy portion J1bw, and a rough uneven shape is formed around the holes BH. In transparent part J1bt, as shown in FIG. 25, the flat surface was formed and the hole part was not formed. In the interference portion J1bi, the substantially uniform hole portions SH are regularly arranged. The dimension of the hole SH is much smaller than that of the hole BH. In addition, traces of melting were observed except for the holes SH.

  Further, as shown in FIG. 27, the inventor has a high linear area LS in a plan view that extends from the cloudy portion J1bw to the interference portion J1bi through the transparent portion J1bt, as shown in FIG. The change in thickness was measured with a surface roughness meter. The measurement results are shown in FIG.

  As shown in FIG. 28, the gradient of the height change is lower in the interference portion J1bi than in the cloudy portion J1bw. Moreover, although the dent part D had arisen in the middle in transparent part J1bt, such a dent part did not arise in interference part J1bi.

(3) Summary After irradiating laser light under the irradiation conditions of this experimental example, the upper test piece J1u and the lower test piece J1b are separated to easily obtain a thin magnesium oxide single crystal substrate with few lattice defects. I was able to.

  Moreover, when performing this separation, it was possible to separate from the modified layer 22 with a significantly small tensile breaking stress as described above. Therefore, it is considered that the surface layer peeling has occurred in the modified layer 22.

  Also, in this separation, the peeling tip position waves in the vertical direction (test piece thickness direction, that is, the thickness direction of the modified layer 22) in the modified layer 22 formed along the horizontal direction (substrate surface direction). It turns out that it peels while being repeated like hitting.

  On the peeling surface J1bs, the transparent portion J1bt, the interference portion J1bi, and the white turbidity portion J1bw appeared in order to form a continuous periodic pattern J1bp, and this continuous direction was in the [01-1] direction.

  Then, from the measurement result of the height change of the periodic pattern, the cloudy portion J1bw occurs near the upper end of the modified layer 22 (on the side irradiated with laser light), and the transparent portion J1bt appears near the lower end of the modified layer 22 (laser It is presumed that the interference portion J1bi occurs at the intermediate portion of the modified layer 22 (an intermediate modified layer thickness direction position between the cloudy portion J1bw and the transparent portion J1bt).

  Then, from the observation result of the peeling surface J1bs by SEM and the measurement result of the surface roughness of the peeling surface J1bs, when irradiating the test piece J1 with the laser beam B, irradiation is performed so as to generate the interference portion J1bi on the peeling surface J1bs. It was determined that it was preferable to make it easy to suppress unevenness on the peeled surface when peeling.

<Experimental example 5>
The present inventor conducted an experiment in which the line pitch rp = 4 mm (see FIG. 20) performed in Experimental Example 4 was changed to the line pitch rp = 7 mm, and was peeled from the modified layer in the same manner as Experimental Example 4 ( Separation of the upper test piece and the lower test piece). As a result, most of the peeling surface of the lower test piece was a transparent portion, and more difficult to peel compared to the case where the line pitch rp = 4 mm.

  For this reason, it is estimated that when the line pitch rp is narrowed, the periodic pattern J1bp tends to appear, and when the line pitch rp is too wide, a transparent portion is likely to occur.

  Then, this inventor examined the generation | occurrence | production cause of the cloudiness part J1bw. Then, the inventor used the test piece J2 cut out from the single crystal magnesium oxide wafer 20u in the same manner as the test piece J1 used in Experimental Example 4, and as shown in FIG. 29, the region where the peeled portion J2s was formed. Were further irradiated with laser light (that is, the same irradiation position was irradiated for the second time), and the surface thereof was observed with SEM. As a result, a white portion W of the image that substantially coincides with the cloudy portion J1bw measured in Experimental Example 4 was observed. Accordingly, the cloudy portions J1uw and J1bw may be clouded by further irradiating the peeled portion with laser light.

  Further, the present inventor cuts the test piece J2 that has been irradiated for the second time in this manner, thereby exposing the cross section of the white portion W, and observed this cross section with an SEM. As a result, as shown in FIG. 30, the image of the white portion W is an image in which the peeling portion J2v is further on the peeling portion J2s that has advanced previously.

<Experimental example 6>
In addition, as shown in FIG. 31, the present inventor conducted an experiment in which irradiation was performed by shifting the position so as not to overlap in the first irradiation and the second irradiation. Specifically, the test piece J3 is arranged such that the irradiation line R2 at the second irradiation of the laser light is positioned at an intermediate position between the adjacent irradiation lines R1 and R1 at the first irradiation of the laser light. Set the position. The test piece J3 is cut out from the single crystal magnesium oxide wafer 20u, similarly to the test pieces J1 and J2. Irradiation conditions are shown in FIG.

  Here, in this experimental example, the line pitch rp1 of the first irradiation (interval between adjacent irradiation lines in the first irradiation) is 8 μm, and the line pitch rp2 of the second irradiation (in the second irradiation). (Interval between adjacent irradiation lines) is also 8 μm. The irradiation line R2 in the second irradiation is located at an intermediate position between the adjacent irradiation lines R1 in the first irradiation. That is, the interval rpm (line pitch between the first and second times) between the irradiation line R1 in the first irradiation and the irradiation line R2 in the second irradiation is 4 μm.

  The irradiated surface side of the test piece J3 after the second laser light irradiation was photographed from above the test piece using an SEM or the like. An imaging result is shown in FIG. In FIG. 33 (a), a line-shaped white portion was observed on a part of the irradiated surface, but no periodic pattern was generated.

  Then, it peeled from the process layer similarly to Experimental example 4, and peeled surface J3s was observed with SEM etc. The imaging results are shown in FIGS. As can be seen from FIG. 35, the shape of the processing mark K1 by the first irradiation was clearly different from the shape of the processing mark K2 by the second irradiation. Particularly in the second irradiation, an annular mark K2c similar to the outer periphery of the hole SH (see FIG. 26) of the interference part J1bi formed in Experimental Example 4, and a square formed so as to surround each annular mark K2c. An outer edge mark K2r was formed. In the peeling surface J3s, the uneven shape is present, but the uneven height is at most about H = 2.62 μm (measurement position is the line U in FIG. 36).

  Since the magnesium oxide single crystal substrate exfoliated according to the present invention can be efficiently formed, the exfoliated substrate obtained from the magnesium oxide single crystal substrate is useful as a high-temperature superconducting film, a ferroelectric film, and the like. It can be applied in a wide range of fields such as display field and energy field.

DESCRIPTION OF SYMBOLS 10 Separation board manufacturing apparatus 14 Laser condensing means 15 Condensing lens 16 First lens 18 Second lens 20 Magnesium oxide single crystal substrate (single crystal substrate)
20p release substrate 20r irradiated surface 20u single crystal magnesium oxide wafer (single crystal substrate)
32 Modified layer B Laser beam K Processing mark Kp Processing mark separation part J3s Release surface R1 Irradiation line R2 Irradiation line dp Dot pitch rp Line pitch

Claims (5)

A first step of disposing laser condensing means for condensing laser light in a non-contact manner on an irradiated surface of a magnesium oxide single crystal member;
Using the laser condensing means, the laser condensing means, the single crystal member, A substrate manufacturing method comprising: a second step of sequentially forming planar marks by sequentially forming processing traces by relatively moving two-dimensionally.   The substrate manufacturing method according to claim 1, wherein the laser beam is a high-intensity laser beam. A first step of disposing laser condensing means for condensing laser light in a non-contact manner on an irradiated surface of a magnesium oxide single crystal member;
Using the laser condensing means, the laser condensing means, the single crystal member, A second step of sequentially forming processing marks in the single crystal member by relatively moving the two-dimensionally,
Using the laser condensing means, the laser condensing means, the single crystal member, Are moved in a two-dimensional manner to cause surface peeling by sequentially irradiating laser light between adjacent irradiation lines when irradiated in the second step. A substrate manufacturing method comprising the steps of:   4. The substrate manufacturing method according to claim 3, wherein in the third step, laser light is sequentially irradiated to an intermediate position between adjacent irradiation lines when irradiated in the second step. In the second step and the third step, a modified layer is formed by arranging the processing marks in a planar shape,
When the planar peeling is sequentially generated, a uniform processing mark separation portion formed by separating the processing marks is formed on the separation surface of the modified layer on the side opposite to the irradiated side. The substrate manufacturing method according to claim 3, wherein the substrate is peeled off as described above.